In recent years, as mobile terminals (user equipment), which include a number of wireless interfaces for 3G communication, Wi-Fi communication, etc., have increased, Multipath Transmission Control Protocol (MPTCP) for UE to recognize and use a number of network links in Transport Layer has increased in importance.
The MPTCP refers to a technology that allows a Transmission Control Protocol (TCP) session to use multiple paths, thereby increasing the reliability and the TCP throughput due to diversity, compared with an existing single path TCP.
FIG. 1 illustrates diagrams showing a method of transmitting/receiving data based on an MPTCP in a conventional wireless communication system.
As shown in diagram (a) of FIG. 1, the transmitter 100 is capable of transmitting data packets to the receiver 120 via a number of paths. More specifically, the transmitter 100 is capable of transmitting: “9, 8, 6, and 4” of the data packets “9, 8, 7, 6, 5, and 4” to the receiver 120 via one of the two paths, i.e., a first path 110; and “7 and 5” to the receiver 120 via the other path, i.e., a second path 120.
Alternatively, as shown in diagram (b) of FIG. 1, in order to prevent data packets from being lost during the transmission, the transmitter 100 may transmit the same data packets to the receiver 120 via the two paths 110 and 130. That is, the transmitter 100 transmits: data packets “7, 5, 9, 8, 6, and 4” to the receiver 120 via the first path 110; and the same as part of the data packets transmitted via the first path 110, e.g., “7 and 5”, to the receiver 120 via the second path 130.
In this case, although the data packets transmitted via the second path 130 are lost, since the receiver 120 may receive the entire data packets via the first path 110, it can perform a successful data decoding process.
However, the wireless communication system using an MPTCP may have a problem of reduction of TCP throughput due to packet loss that may occur in individual paths. This is because the TCP window size is reduced by out-of-order data packets which are created due to loss of packets.
In addition, the wireless communication system using an MPTCP has paths that differ in quality from each other and this may cause transmission delay of data packets. Transmission delay of data packets causes latency in the data decoding process. Therefore, the data throughput is reduced.
In this case, although one or more of the packets in transmission or reception are not normally transmitted, in proportion to Packet Loss Rate (PLR) of UE, the technology may add redundancy to packet data in order to easily decode the packets received by UE and transmit/receive the packets. When transmitting/receiving data with a redundancy, although part of the packets are lost, the transmitted data may be successfully restored according to the redundancy value. When data packets are processed to contain a redundancy and transmission/reception of the signals is performed, the base station or Access Point (AP) may have a problem of increasing the load according to an encoding process for the addition of redundancy. In addition, in order to perform transmission/reception of data in response to different PLRs according to UE devices, radio resources of which amount is limited may be excessively used.
Therefore, a method and apparatus is required to solve these problems.